Cutting insert

ABSTRACT

A cutting insert of the indexable type comprises intersecting surfaces which form a pair of chip control channels associated with a respective cutting edge. The channels merge at respective corners and terminate at the intermediate land portion which is arcuate and at an angle of ninety degrees or greater to a respective side surface.

The present invention relates to disposable cutting inserts,particularly to cutting inserts such as are adapted for being detachablymounted on a tool holder and for cutting a work piece.

Cutting inserts of a type referred to are generally made of a cementedmetal carbide and are formed by pressing techniques after which thepressed articles are sintered.

In the type of inserts referred to herein, it is desirable to have anindexable insert which presents a positive rake cutting edge to the workpiece. Inserts of this type are described in the following discussedpatents.

U.S. Pat. No. 3,487,515 to Contrucci discloses an insert having top andbottom supporting surfaces comprising an island spaced inward from theperipheral sides adjacent the cutting points and extending out to theperipheral sides intermediate the cutting points to increase thestability of support for the insert.

U.S. Pat. No. 3,885,281 to Stambler discloses an insert having bothlongitudinally curved and transversely curved channels along the sideedges of the insert meeting at the corners of the insert. At each cornerof the insert, V-shaped shallow grooves are depressed into the mergingportions of the deeper longitudinal channels to provide chip control forshallow depth cuts.

U.S. Pat. No. 3,882,580 to Lundgren describes a cutting insert of thetype having a longitudinal groove extending entirely around the insertadjacent the side surfaces wherein an inactive portion of the cuttingedge has a continuously decreasing rake angle.

U.S. Pat. No. 3,786,541 to Lundgren relates to a cutting insert havingchip breakers in two stages wherein the cutting edge and the associatedchip breaker describe a curve of a particular description.

U.S. Pat. No. 4,056,872 which issued to the inventor of the presentapplication, relates to an insert having inner and outer portions of thechip breaking channel being provided with straight faces.

U.S. Pat. No. 3,792,515 to Lundgren relates to a cutting insert whereinthe cutting edge and associated chip-breaker describe a curve composedof straight or arched parts in the plane of the side face.

U.S. Pat. No. 3,786,540 describes an insert having chip control grooveextending along a side surface. The width of the groove describes acompound curve such that the width varies along the length of the sidein such a manner that the width at the midpoint of the side is less thanthe width which points intermediate the midpoint and at the ends of theside.

U.S. Pat. No. 3,399,442 to Jones describes an insert having chip controlgroove along the entire outer edge comprises an inner and outer region.The outer region is concave in cross section.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a cuttinginsert comprising a polygonal body having substantially parallelsurfaces and peripheral side surfaces substantially normal to saidparallel surfaces joining to form corners of said parallel surfacesjoining to form corners of said polygon, at least one of said parallelsurfaces having grooved recesses merging at and descending fromrespective corners of said polygon addjacent respective peripheral sidesurfaces, inner land portions extending downwardly and outwardly from arespective parallel surface toward a respective side surface, each innerland portion comprising a pair of end face portions joining anintermediate face portion, each of said grooved recesses including arespective end face and adjoining outer land portion, said adjoiningouter land portion extending inwardly and downwardly at an acute anglefrom a side surface to form a cutting edge therewith, each side surfacehaving associated therewith a pair of adjoining outer land portions andan intermediate land portion, said intermediate land portion beingarcuate and extending inwardly from a respective side surface to saidintermediate face portion at an angle of ninety degrees or greater tosaid respective side surface, said pair of adjoining outer lands mergingwith said intermediate land for terminating respective grooves.

DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of one embodiment of the preferredinvention;

FIG. 2 is a top plan view of the embodiment of FIG. 1; and

FIG. 3 is a side elevational view of the embodiment as shown in FIG. 2.

DETAILED DESCRIPTION

With reference to FIG. 1, there is illustrated a cutting insert 11 inaccordance with the preferred embodiment of the present invention. Asshown, the cutting insert 11 comprises a polygonal body havingsubstantially parallel surfaces 15, 17 in the form of respective upperand lower surfaces and peripheral side surfaces 19 substantially normalto the upper and lower surfaces 15, 17. The side surfaces 19 meet toform corners 20 at the ends of the side surfaces 19. At least one of theparallel surfaces 15, 17 has chip control channels or grooved recesses21 merging at and descending from each of the respective corners 20 ofthe polygon. Channels 21 extend adjacent the peripheral side surfaces19. Although the insert 11 shown in the drawings is triangular in shape,it is contemplated that the insert 11 may be in the shape of any polygonsuch as square, diamond or rectangular.

As further illustrated in FIG. 1, the insert 11 includes a plurality ofplanar outer land portions 25 associated with and forming at least apair of cutting edges 26, 28 with each side surface 19. Cutting edges26, 28 are formed by the intersection of each of the outer land portions25 with a respective side surface 19. Each of the outer land portions 25forms an angle less than 90° or an acute angle with an adjacentperipheral side surface 19. This first direction is downwardly towardthe interior of the insert 11 within a plane normal to a peripheral sidesurface 19. The slope of the outer lands 25 in the first directionimparts a positive rake angle to the cutting edges 26, 28.

Each of the outer lands 25 descend downwardly in a second direction fromone of the corners 20 along respective peripheral side surfaces 19toward an adjacent one of the corners 20. When the outer land portions25 are observed from a planar view as illustrated in FIG. 3, each of theouter land portions 25 extends downwardly in the second direction at anacute angle from a respective corner 20. This angle is shown as angle ain FIG. 2. This second direction is normal to the first directionhereinbefore discussed. It is preferred that angle "a" is of about 6°.The slope of outer lands 25 in the second direction influences thedirection of chip flow.

As a continuation of the above described cutting edges 26, 28, anintermediate edge 30 is formed by the intersection of an intermediateland 32 with a respective side surface 19. As illustrated in FIG. 3, theintermediate land 32 extends inwardly at an angle of 90° or greater froma respective side surface 19.

An inner land portion 23 extends downwardly and outwardly from arespective surface 15, 17 toward a respective side surface 19. Eachperipheral side surface 19 has an inner land portion 23 associatedtherewith and spaced inwardly therefrom. Each of the inner land 23comprises a pair of end face portions 31, 32 joining a singleintermediate face portion 45. The one end of the end portions 31, 32 arespaced inwardly from the polygonal corners 20 and rise above the mergingouter land portions 25 near the corners 20. The other ends of end faceportions 31, and conjunctively join the intermediate face portion 43 soas to bridge the intersecting end face portions 31 and 32. The commonjuncture 33 is inward of the intermediate face portion 43. The innerland portion 23 at the intermediate face portion 43 is closer to theperipheral side than would be the case if the inner land portion 23 wereformed only by insecting outer face portions 31, 32.

The face portions 31, 32 lie substantially in planes which intersect ata first common juncture 33 which extends downwardly from a respectiveparallel surface toward the interior of the insert 11. With reference toFIG. 2, it can also be seen that intersection of face portion 31 withsurface 15 forms an angle "b" with side surface 19 of about 6° . Theadjoining plane of faced portion 32 similarly forms this angle with aside surface 19 but in an opposing manner to that illustrated for faceportion 31.

The end face portions 31, 32 join one of the respective outer landportions 25 for forming the channels 21 which are associated withrespective cutting edges 26, 28. Each of the cutting edges 26, 28 ashereinbefore described has one of the respective channels 21 adjacent toand extending along a length thereof. As illustrated in FIG. 2, thechannels 21 terminate at the junction of the outer land portion 25 withthe intermediate land portion 32. Thus, the chip control channelnormally associated with an insert of this type as described in U.S.Pat. No. 4,056,872 is interrupted at a central portion of the cuttingedge and does not extend entirely around the periphery of the insert 11.

The intermediate land portion 32 which is interposed outer land portions25 is formed as an arcuate shaped dip. The intermediate land portion 32is connected to and joins respective outer land portions 25 at junctionregions 41. Preferably at least a portion of the intermediate landportion 32 is formed below the intersecting planes of the outer landportions 25. The junction regions 41 may be formed in a variety ofconstructions. As illustrated in FIG. 1, the junction regions 41 extendrearwardly from the peripheral side 19 along merging paths. It iscontemplated that the junction regions may extend rearwardly alongparallel or diverging paths. The junction regions 41 which blenddifferent lands may be in the form of a fillet with the intermediateland portion 32 merging gradually into the outer land portions 25.

At least a portion of outer land portions 25 lie in respective planeswhich intersect at a second common juncture 37 shown as a dotted line inFIG. 3. The line 37 is formed by an extension of the respective planes.The common junctures 33 and 37 meet in an adjoining relationship andform an angle therebetween. The preferred angle of the junctures 33 and37 is within the range of from 120° to about 140°. Each of the describedjunctures 33 and 37 are substantially centrally located from the ends ofa respective side.

The insert 11 includes a central opening 40 extending therethrough tofacilitate positioning the insert 11 in a tool holder. The opening 40provides a means whereby a mating member can be fitted within theopening 40 to secure the insert to the work holder. It is also possibleto use a center post and washer-nut combination to hold the insert inplace in addition to several other well known securing devices. When theinsert 11 of the present invention is positioned in a negative rakeholder of the type wherein the insert is tilted downwardly, the insertof the present invention provides a positive back rake angle to the workpiece along the respective cutting edges 26, 28 eminating from thecorners 19 thereof and a negative back rake angle at the intermediateedge portion 30.

While there have been shown and described what are presently consideredthe preferred embodiments of the present invention, it will be obviousto those skilled in the art that various changes and modifications maybe made therein without departing from the scope of the invention asdefined by the appended claims.

I claim:
 1. A cutting insert comprising a polygonal body havingsubstantially parallel surfaces and peripheral side surfacessubstantially normal to said parallel surfaces joining to form cornersof said polygon, at least one of said parallel surfaces having groovedrecesses merging at and descending from respective corners of saidpolygon adjacent respective peripheral side surfaces, inner landportions extending downwardly and outwardly from a respective parallelsurface toward a respective side surface, each inner land portioncomprising a pair of end face portions joining an intermediate faceportion, each of said grooved recesses including a respective end faceand adjoining outer land portion, said adjoining outer land portionextending inwardly and downwardly at an acute angle from a side surfaceto form a cutting edge therewith, each side surface having associatedtherewith a pair of adjoining outer land portions and an intermediateland portion, said intermediate land portion being arcuate and extendinginwardly from a respective side surface to said intermediate faceportion at an angle of ninety degrees or greater to said respective sidesurface, said pair of adjoining outer lands merging with saidintermediate land for terminating respective grooves.